The present invention relates to processed cheese and methods of making processed cheese. In particular, the invention relates to the use of a protein cross-linking enzyme during the manufacturing process to produce a processed cheese having an improved firmness.
Processed cheese has become a staple of the food industry. It is also a commodity, meaning that there are many suppliers of processed cheese. As a result, the price charged for processed cheese has a great impact on a supplier's share of the market. Thus processed cheese manufacturers are under constant pressure to reduce their costs. On the other hand, government regulations regarding the ingredients that can be used, and the desire for functional qualities such as taste, firmness, mouth feel and meltability, constrain efforts to reduce costs. In addition to the quality perceived by the consumer, functional qualities are also important in the manufacturing process.
One of the efforts to reduce cost for cheese has been to keep the whey proteins from being lost in the cheese making process. For example, U.S. Pat. No. 5,356,639 discloses a process for making cheese by using ultrafiltration and diafiltration to keep all of the whey proteins in the final cheese. Also, U.S. Pat. No. 5,681,598 discloses the use of transglutaminase to cross-link proteins in milk to increase the yield of the curds from the milk. In addition, whey solids are a common ingredient mixed with cheese to make processed cheese. However, the presence of whey solids in processed cheese has a negative impact on the firmness of the processed cheese. Other ingredients that may he added to processed cheese may also have a negative impact on the firmness or meltability of the processed cheese. Also, many other measures taken to reduce cost often have a negative impact on the firmness of processed cheese.
Transglutaminase has been suggested for use in various food products. Transglutaminase cross-links proteins in meat products to improve the hardness and elasticity of the products, as well as to improve the texture of products containing low meat content. Transglutaminase has also been disclosed for use in dairy products. For example, U.S. Pat. No. 6,224,914 discloses a process for incorporating whey proteins into cheese using transglutaminase, and U.S. Pat. No. 6,242,036 discloses cheese curd made using transglutaminase and a non-rennet protease. U.S. Pat. No. 6,270,814 discloses incorporation of whey into process cheese. However, the common problem with many of these processes is that transglutaminase is currently fairly expensive. Thus, the benefit it provides is not worth its cost. None of the foregoing processes using transglutaminase are believed to be currently used on a commercial basis in the United States.
Another approach for utilizing transglutaminase in processed cheese is disclosed in Japanese Patent Publication No. 2594340. In the disclosed process, cheese and other ingredients are melted, mixed together and cooked to make a processed cheese. The temperature is then reduced and transglutaminase is added and allowed to act on the melted cheese mixture to produce a product with optimal stringiness and high temperature shape retention. One problem with this process is that the processed cheese is stirred at a medium temperature, such as 50° C. (122° F.), for 30 minutes while the transglutaminase reacts. This material then has to be reheated to 85° C. (185° F.) to deactivate the transglutaminase. All of this post-manufacture processing of the processed cheese is impractical in making a commodity processed cheese, which otherwise requires only a very short residence time in the mixing and cooking equipment.
Hence, there is still a need for a process for making processed cheese that has good firmness, but which is commercially practical. Also, a processed cheese that is inexpensive, but still has good firmness and melt properties would be highly desirable.